Architectural Changes of the Gastrocnemius Muscle after Botulinum Toxin Type A Injection in Children with Cerebral Palsy

Abstract

PurposeThis study used ultrasonography (US) to investigate the architectural changes in gastrocnemius muscles (GCM) after botulinum toxin injection (BoNT-A) in children with cerebral palsy (CP).Materials and MethodsThirteen children with CP who received a BoNT-A injection into their GCM to treat equinus were recruited (9 males and 4 females). Architectural changes in both the medial and lateral heads of the GCM from a total of 20 legs were assessed using B-mode, real-time US. Muscle thickness (MT), fascicle length (FL), and fascicle angle (FA) were measured over the middle of the muscle belly in both a resting and neutral ankle position. Measures at 1 and 3 months after the injection were compared with baseline data taken before the injection.ResultsThe mean age of the subjects was 5.8 (±1.6) years. Spasticity was significantly reduced when measured by both the modified Tardieu scale and the modified Ashworth scale at 1 and 3 months after injection (p<0.05). The MT and FA of both the medial and lateral heads of the GCM were significantly reduced for both neutral and resting ankle positions at 1 and 3 months after the injection. The FL of both the medial and lateral heads of the GCM were significantly increased in a resting position (p<0.05), but not in a neutral position.ConclusionOur results demonstrated muscle architectural changes induced by BoNT-A injection. The functional significances of these changes were discussed.

Muscle volume alterations after first botulinum neurotoxin A treatment in children with cerebral palsy: a 6‐month prospective cohort study

“…The magnitude of this absolute reduction was less than that identified in previous research. At 4 and 13 weeks after injection, the current study identified reductions of 5.9% and 9.4%, compared with 11.2% and 17.6% by Park et al, a difference attributed to the measurement method used, with Park et al using muscle thickness as a substitute for muscle volume. At 25 weeks, the 6.8% reduction in muscle volume is notably less than the 13.8% reduction found by Van Campenhout et al This discrepancy may be explained by the different muscle assessed (the psoas muscle, markedly different in its operating characteristics compared with the gastrocnemius) and the ambulatory status of the participants (which was not stated).…”

“…Recent research has provided evidence to support the hypothesis that BoNT‐A exposure among children with CP is associated with impaired muscle growth in the short term. BoNT‐A exposure results in atrophy of between 4.47% and 20.5% of injected muscle, between 5 and 12 weeks after injection, depending on the muscle assessed and the measurement technique used . While the pharmacological effect of BoNT‐A washes out by approximately 12 weeks, it is important to understand the long‐term impact beyond this period.…”

“…BoNT-A exposure results in atrophy of between 4.47% and 20.5% of injected muscle, between 5 and 12 weeks after injection, depending on the muscle assessed and the measurement technique used. [11][12][13] While the pharmacological effect of BoNT-A washes out by approximately 12 weeks, 14 it is important to understand the long-term impact beyond this period. Studies have identified atrophy of injected psoas of 13.8% at 6 months, 11 and hypertrophy of injected gastrocnemius of 13% at 12 months 15 in children with CP, although the authors noted this rate of growth was reduced compared with typically developing children.…”

Comprehensive evaluation of gait, spasticity, and muscle morphology: A case report of a child with spastic paresis treated with Botulinum NeuroToxin‐A, serial casting, and physiotherapy

“…The physiological cross‐sectional area ( A fasc ) of the GM marginally increased after treatment. It is generally presumed that BoNT‐A injections combined with serial casting improve the extensibility of triceps surae muscles by reducing muscular hyperactivity, by atrophy, and by length adaptations of muscle fibers . Muscle atrophy implies a reduction in the number of titin filaments arranged in parallel, which is associated with reduced resistance to extension .…”

Foot deformities in children with cerebral palsy

“…It was recently suggested [6] that Botox injections may result in loss of muscle volume and in architectural changes of the injected muscle, possibly leading to a decreased capacity for force generation and impaired function. This can be accomplished by a neurosurgical procedure called rhizotomy, which entails selectively cutting the afferent nerve rootlets in the lumbar spine, or intramuscular injections of botulinum toxin.…”